Liquid crystal display

ABSTRACT

A liquid crystal display includes an array pixel including a plurality of pixels arranged in a matrix. The plurality of pixels include a set of pixels including a pair of center pixels adjacent to each other, and a pair of first-color pixels and a pair of second-color pixels obliquely facing each other across the center pixels. Each pixel includes a pixel electrode and a thin film transistor. The liquid crystal display further includes a plurality of gate lines extending in a row direction for transmitting a gate signal to the pixels, and a plurality of data lines extending in a column direction for transmitting data signals to the pixels. The pixels are subject to polarity inversion.

BACKGROUND OF THE INVENTION

(a) Field of the Invention

The present invention relates to a liquid crystal display.

(b) Description of Related Art

Generally, a liquid crystal display (LCD) includes a liquid crystalpanel assembly including two panels provided with two kinds of fieldgenerating electrodes such as pixel electrodes and a common electrodeand a liquid crystal layer with dielectric anisotropy interposedtherebetween. The variation of the voltage difference between the fieldgenerating electrodes, i.e., the variation in the strength of anelectric field generated by the electrodes changes the transmittance ofthe light passing through the LCD, and thus desired images are obtainedby controlling the voltage difference between the electrodes.

The LCD includes a plurality of pixels with pixel electrodes and red(R), green (G) and blue (B) color filters. The pixels are driven toperform display operation by way of the signals applied thereto throughdisplay signal lines. The signal lines include gate lines (or scanningsignal lines) for carrying the scanning signals, and data lines forcarrying data signals. Each pixel has a thin film transistor (TFT)connected to one of the gate lines and one of the data lines to controlthe data signals applied to the pixel electrode.

Meanwhile, there are several types of arrangement of the red (R), green(G) and blue (B) color filters. Examples are a stripe type where thecolor filters of the same color are arranged in the same pixel columns,a mosaic type where the red, green and blue color filters are arrangedin turn along the row and column directions, and a delta type where thepixels are arranged zigzag in the column direction and the red, greenand blue color filters are arranged in turn. The delta type correctlyrepresents a circle or a diagonal line.

The ClairVoyante Laboratories has proposed a pixel arrangement calledthe “PenTile Matrix.,” which is advantageous in displaying highresolution images while gives minimized design cost. In such a pixelarrangement, the unit pixel of blue is common to two dots, and theneighboring blue pixels receive the data signals from one data drivingIC while being driven by two different gate driving ICs. With the use ofthe PenTile Matrix pixel structure, the resolution of the ultra extendedgraphics array (UXGA) level can be realized by way of a display deviceof the super video graphics array (SVGA) level. Furthermore, the numberof low-cost gate driving ICs is increased, but the number of high-costdata driving ICs is decreased. This minimizes the production cost forthe display device.

However, with the PenTile Matrix pixel structure, as the size of theblue pixel is different from the size of the red and the green pixels,it is required to make alteration of the storage capacity due to thedifference in the liquid crystal charge rate. Furthermore, as two bluepixels are driven by way of one line, the pixel polarities arenon-uniformly made.

SUMMARY OF THE INVENTION

A liquid crystal display is provided, which includes: an array of aplurality of sets of pixels, each set including blue and white pixelsadjacent to each other, a pair of red pixels obliquely facing each otheracross the blue and the white pixels, and a pair of green pixelsobliquely facing each other across the blue and the white pixels andadjacent to the red pixels, each pixel including a pixel electrode and athin film transistor; a plurality of gate lines extending in a rowdirection for transmitting a gate signal to the pixels; and a pluralityof data lines extending in a column direction for transmitting datasignals to the pixels.

It is preferable that the blue pixel and the white pixel in a set ofpixels have equal polarity, the red pixels in the set have equalpolarity, and the green pixels in the set have equal polarity. Thepolarity of the pixels may be subject to column inversion or 2×1inversion.

Alternatively, it is preferable that the blue pixel and the white pixelin a set of pixels have equal polarity, the red pixels in the set haveopposite polarity, and the green pixels in the set have oppositepolarity. The polarity of the pixels may be subject to 2×1 inversion.

The relative positions of the blue pixel and the white pixel in two setsof pixels adjacent in a column direction or in a row direction arereversed.

The pixels have rectangular shapes and the blue and the white pixels arearranged in the column direction to form a separate column or the blueand the whit pixels have triangular shapes to form a diamond shape. Aboundary line between the blue pixel and the white pixel may extend inthe row direction or the column direction.

The red pixels in adjacent two columns may be located in different rowsand the red pixels in adjacent rows are located in different columns.The green pixels in adjacent two columns are placed in different rowsand the green pixels in adjacent rows are located in different columns.Either the blue pixels or the white pixels in two sets of pixelsadjacent in the row direction are located in different rows, or the bluepixels or the white pixels in two sets adjacent in the column directionare located in different columns.

The liquid crystal display is preferably driven by rendering.

The liquid crystal display may further include a backlight unitproviding light for the pixels. The light emitted from the backlightunit preferably has a color coordinate (x, y) where x ranges from about0.31 to about 0.34, and y ranges from about 0.32 to about 0.35.

The red, green and blue pixels may further include red, green and blueorganic filters containing red, green and blue pigments, respectively,and the white pixels may include transparent organic filters.

The red, green, blue and white pixels may further include a commonelectrode formed on the organic filters and/or an overcoat locatedbetween the organic filters and the common electrode.

The transparent organic filter may include the same material as theovercoat.

Preferably, the height of a surface of the overcoat is substantiallyuniform.

The red, green, blue and white pixels may further include red, green andblue color filters, respectively. The red, green, blue and white pixelsfurther include: a protective layer formed on the thin film transistors,having a plurality of protrusions, and facing the color filters; acommon electrode formed on the color filters; and a liquid crystalinterposed between the pixel electrode and the common electrode. Theprotrusions are provided in the white pixels, and height of the commonelectrode is smaller at the white pixel than at the red, the green andthe blue pixels.

Preferably, the distance between the common electrode and a surface ofthe protective layer is substantially uniform.

The pixel electrodes and the common electrode may have cutouts.

A liquid crystal display is provided, which includes: an array pixelincluding a plurality of pixels arranged in a matrix, the plurality ofpixels including a set of pixels including a pair of center pixelsadjacent to each other, and a pair of first-color pixels and a pair ofsecond-color pixels obliquely facing each other across the centerpixels, each pixel including a pixel electrode and a thin filmtransistor; a plurality of gate lines extending in a row direction fortransmitting a gate signal to the pixels; and a plurality of data linesextending in a column direction for transmitting data signals to thepixels, wherein the pixels are subject to polarity inversion.

The center pixels in a set of pixels have equal polarity, thefirst-color pixels in the set have equal polarity, and the second-colorpixels in the set have equal polarity.

The polarity inversion includes column inversion or 2×1 inversion.

The center pixels in a set of pixels have equal polarity, thefirst-color pixels in the set have opposite polarity, and thesecond-color pixels in the set have opposite polarity.

The polarity inversion may include 2×1 inversion.

The center pixels represent blue color, and the first-color pixels andthe second-color pixels represent green and red colors, respectively.Alternatively, the center pixels represent red color, and thefirst-color pixels and the second-color pixels represent green and bluecolors, respectively. Alternatively, the center pixels represent blueand white colors, and the first-color pixels and the second-color pixelsrepresent green and red colors, respectively.

The center pixels may have different saturation, and the center pixelspreferably represent red color.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other advantages of the present invention will become moreapparent by describing preferred embodiments thereof in detail withreference to the accompanying drawings in which:

FIG. 1 is a block diagram of an LCD according to an embodiment of thepresent invention;

FIG. 2 is an exploded perspective view of an LCD according to anembodiment of the present invention;

FIG. 3 is an equivalent circuit diagram of a pixel of an LCD accordingto an embodiment of the present invention;

FIGS. 4A and 5A illustrate spatial arrangements of pixels of LCDsaccording to embodiments of the present invention;

FIGS. 4B and 5B illustrates a group of pixels forming a dot, which is anelementary unit for an image in the pixel arrangements shown in FIGS. 4Aand 5A, respectively;

FIG. 6 is an exemplary pixel group for a rendered LCD according to anembodiment of the present invention;

FIG. 7 is a layout view of an exemplary TFT array panel for an LCDaccording to an embodiment of the present invention;

FIG. 8 is a sectional view of the TFT array panel shown in FIG. 7 takenalong the line VIII-VIII′;

FIG. 9 is a layout view of an exemplary TFT array panel for an LCDaccording to another embodiment of the present invention;

FIGS. 10A and 10B are sectional views of the TFT array panel shown inFIG. 9 taken along the line XA-XA′ and the line XB-XB′, respectively;

FIG. 11 is a sectional view of an LCD according to another embodiment ofthe present invention;

FIGS. 12 to 15 illustrate pixel arrangements of LCDs according toembodiments of the present invention;

FIG. 16 is a graph showing an exemplary light spectrum of a light sourceaccording to an embodiment of the present invention.

FIGS. 17 and 18 are sectional views of color filter array panels for anLCD according to other embodiments of the present invention;

FIG. 19 is a graph illustrating the response time as a function of thecell gap of an LCD;

FIG. 20 is a sectional view of an LCD according to another embodiment ofthe present invention;

FIGS. 21 to 23 illustrate pixel arrangements for an LCD according toother embodiments of the present invention;

FIG. 24 is a picture for illustrating the visibility of an LCD havingthe pixel arrangement shown in FIG. 21;

FIG. 25 is a layout view of a TFT array panel for an LCD according toanother embodiment of the present invention;

FIG. 26 is a sectional view of the TFT array panels shown in FIG. 25taken along the line XXVI-XXVI′; and

FIGS. 27 to 29 illustrate various polarity inversions of an LCDaccording to embodiment of the present invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

The present invention now will be described more fully hereinafter withreference to the accompanying drawings, in which preferred embodimentsof the inventions are shown.

In the drawings, the thickness of layers and regions are exaggerated forclarity. Like numerals refer to like elements throughout. It will beunderstood that when an element such as a layer, region or substrate isreferred to as being “on” another element, it can be directly on theother element or intervening elements may also be present. In contrast,when an element is referred to as being “directly on” another element,there are no intervening elements present.

Now, LCDs according to embodiments of this invention will be describedin detail with reference to the accompanying drawings.

FIG. 1 is a block diagram of an LCD according to an embodiment of thepresent invention, FIG. 2 is an exploded perspective view of an LCDaccording to an embodiment of the present invention, and FIG. 3 is anequivalent circuit diagram of a pixel of an LCD according to anembodiment of the present invention.

Referring to FIG. 1, an LCD according to an embodiment of the presentinvention includes a LC panel assembly 300, a gate driver 400 and a datadriver 500 which are connected to the panel assembly 300, a gray voltagegenerator 800 connected to the data driver 500, a lighting unit 900 forilluminating the panel assembly 300, and a signal controller 600controlling the above elements.

In structural view, the LCD according to an embodiment of the presentinvention includes a LC module 350 including a display unit 330 and abacklight unit 340, as shown in FIG. 2.

The display unit 330 includes the LC panel assembly 300, a plurality ofgate flexible printed circuit (FPC) films 410 and a plurality of dataFPC films 510 attached to the LC panel assembly 300, and a gate printedcircuit board (PCB) 450 and a data PCB 550 attached to the associatedFPC films 410 and 510, respectively.

The LC panel assembly 300, in structural view shown in FIGS. 2 and 3,includes a lower panel 100, an upper panel 200 and a liquid crystallayer 3 interposed therebetween while it includes a plurality of displaysignal lines G₁-G_(n) and D₁-D_(m) and a plurality of pixels connectedthereto and arranged substantially in a matrix in circuital view shownin FIGS. 1 and 3.

The display signal lines G₁-G_(n) and D₁-D_(m) are provided on the lowerpanel 100 and include a plurality of gate lines G₁-G_(n) transmittinggate signals (called scanning signals) and a plurality of data linesD₁-D_(m) transmitting data signals. The gate lines G₁-G_(n) extendsubstantially in a row direction and are substantially parallel to eachother, while the data lines D₁-D_(m) extend substantially in a columndirection and are substantially parallel to each other.

Each pixel includes a switching element Q connected to the displaysignal lines G₁-G_(n) and D₁-D_(m), and an LC capacitor C_(LC) and astorage capacitor C_(ST) that are connected to the switching element Q.The storage capacitor C_(ST) may be omitted if unnecessary.

The switching element Q such as a TFT is provided on the lower panel 100and has three terminals: a control terminal connected to one of the gatelines G₁-G_(n); an input terminal connected to one of the data linesD₁-D_(m); and an output terminal connected to the LC capacitor C_(LC)and the storage capacitor C_(ST).

The LC capacitor C_(LC) includes a pixel electrode 190 on the lowerpanel 100, a common electrode 270 on the upper panel 200, and the LClayer 3 as a dielectric between the electrodes 190 and 270. The pixelelectrode 190 is connected to the switching element Q, and the commonelectrode 270 covers the entire surface of the upper panel 100 and issupplied with a common voltage Vcom. Alternatively, both the pixelelectrode 190 and the common electrode 270, which have shapes of bars orstripes, are provided on the lower panel 100.

The storage capacitor C_(ST) is an auxiliary capacitor for the LCcapacitor C_(LC). The storage capacitor C_(ST) includes the pixelelectrode 190 and a separate signal line (not shown), which is providedon the lower panel 100, overlaps the pixel electrode 190 via aninsulator, and is supplied with a predetermined voltage such as thecommon voltage Vcom. Alternatively, the storage capacitor C_(ST)includes the pixel electrode 190 and an adjacent gate line called aprevious gate line, which overlaps the pixel electrode 190 via aninsulator.

For color display, each pixel represents its own color by providing oneof a plurality of color filters 230 in an area occupied by the pixelelectrode 190. The color filter 230 shown in FIG. 3 is provided in thecorresponding area of the upper panel 200. Alternatively, the colorfilter 230 is provided on or under the pixel electrode 190 on the lowerpanel 100.

Preferably, the color of the color filter 230 is one of the primarycolors such as red, green and blue. Hereinafter, a pixel is referred toas red, greed or blue pixel based on the color represented by the pixeland indicated by reference numerals R, G or B.

Referring to FIG. 2, the backlight unit 340 includes a plurality oflamps 341 illuminating light, a light guide 342 and a plurality ofoptical sheets 343 disposed under the panel assembly 300 and guiding anddiffusing light from the lamps 341 to the panel assembly 300, areflector 344 disposed under the lamps 341 and reflecting the light fromthe lamps 341 toward the panel assembly 300, and a pair of lamp covers345 covering the lamps. The lamps 341 and the lamp covers 345 aredisposed at lateral sides of the light guide 342.

The lamps 341 are illustrated as the lighting unit 900 and preferablyinclude fluorescent lamps such as CCFL (cold cathode fluorescent lamp)and EEFL (external electrode fluorescent lamp). An LED is anotherexample of the lamp 341.

A pair of polarizers (not shown) polarizing the light from the lamps 341are attached on the outer surfaces of the panels 100 and 200 of thepanel assembly 300.

FIGS. 4A and 5A illustrate spatial arrangements of pixels of LCDsaccording to embodiments of the present invention.

Referring to FIGS. 4A and 5A, a plurality of pixels having substantiallyequal size are arranged in a matrix including a plurality of pixel rowand a plurality of pixel columns.

Each pixel row includes pixels representing three colors, i.e., redpixels R, green pixels G, and blue pixels B. The sequence of the pixelsin a pixel row shown in FIG. 4A is the red pixel R, the blue pixel B,and the green pixel G or the green pixel G, the blue pixel B, and thered pixel R. On the contrary, the sequence of the pixels in a pixel rowshown in FIG. 5A is the blue pixel B, the red pixel R, and the greenpixel G or the green pixel G, the red pixel R, and the blue pixel B.

The pixel columns include a plurality of bicolor columns and a pluralityof unicolor columns. As shown in FIG. 4A, each bicolor column includesred pixels R and green pixels G and each unicolor column includes bluepixels B. As shown in FIG. 5A, each bicolor column includes blue pixelsB and green pixels G and each unicolor column includes red pixels R.

When viewing only bicolor columns, any two pixels adjacent to each otherin a row direction or a column direction represent different colors andthus the bicolor columns form a checkerboard pattern. Each unicolorcolumn is interposed between the bicolor columns.

FIGS. 4B and 5B illustrates a group of pixels forming a dot, which is anelementary unit for an image in the pixel arrangements shown in FIGS. 4Aand 5A, respectively.

Each group includes six pixels, i.e., two adjacent center pixels in aunicolor column and four pixels in bicolor columns, which are adjacentto the respective center pixels in the row direction.

An LCD having the above-described pixel arrangement are rendered forincreasing resolution and this will be described in detail withreference to FIG. 6.

FIG. 6 is an exemplary pixel group for a rendered LCD according to anembodiment of the present invention.

Referring to FIG. 6, an exemplary pixel group for rendering is centeredon any pixel P1 in a bicolor pixel. The pixel group includes four pixelsP2 in bicolor columns and two pixels in a unicolor column, which areadjacent to the center pixel P1. The rendering may give about halfweight to the center pixel P1.

In the meantime, since the pixels representing the same colors inbicolor columns face each other obliquely in a symmetrical manner asshown in FIGS. 4B, 5B and 6 and are seen as mixed. On the contrary, thepixels in unicolor columns are arranged in stripes and do not makesymmetry with the pixels in the bicolor columns, which may causeincomplete color mixture and deteriorate image quality. In particular,the bicolor columns shown in FIG. 4B represent green and red, which aremixed to form yellow. Since yellow has luminosity higher than blue, thebicolor columns may be seen brighter than the unicolor columns. On thecontrary, blue and green in the bicolor columns shown in FIG. 5B aremixed to form cyan, which has similar luminosity to red, and thus thebrightness difference may not be detected.

The brightness difference may be much reduced by differentiatingsaturation of two pixels in two adjacent red pixels R in a unicolorcolumn shown in FIG. 5B.

For example, the saturation of a red pixel R right to a blue pixel B andleft to a green pixel G is lower than that of a red pixel R left to ablue pixel B and right to a green pixel G. The red pixel R right to arelatively dark, blue pixel B has lower saturation but higher luminositythan the blue pixel B, while the red pixel B right to a relativelybright, green pixel G has higher saturation but lower luminosity thanthe green pixel G. Accordingly, the brightness difference between twoadjacent pixels in the row direction and the column direction isreduced.

The saturation difference may be obtained by differentiating the amountof pigment mixed to photoresist to form color filters 230 shown in FIG.1. However, other methods may be also used for the saturationdifference.

An exemplary detailed structure of a TFT array panel for an LCDaccording to an embodiment of the present invention will be describedwith reference to FIGS. 7 and 8.

FIG. 7 is a layout view of an exemplary TFT array panel for an LCDaccording to an embodiment of the present invention, and FIG. 8 is asectional view of the TFT array panel shown in FIG. 7 taken along theline VIII-VIII′.

A plurality of gate lines 121 for transmitting gate signals are formedon an insulating substrate 110. Each gate line 121 extends substantiallyin a transverse direction and a plurality of portions of each gate line121 form a plurality of gate electrodes 123. Each gate line 121 includesa plurality of expansions 127 protruding downward.

The gate lines 121 include a low resistivity conductive layer preferablymade of Ag containing metal such as Ag and Ag alloy or Al containingmetal such as Al and Al alloy. The gate lines 121 may have amultilayered structure including a low resistivity conductive layer andanother layer preferably made of Cr, Ti, Ta, Mo or their alloys such asMoW alloy having good physical, chemical and electrical contactcharacteristics with other materials such as ITO (indium tin oxide) andIZO (indium zinc oxide). A good exemplary combination of such layers isCr and Al—Nd alloy.

The lateral sides of the gate lines 121 are tapered, and the inclinationangle of the lateral sides with respect to a surface of the substrate110 ranges about 30-80 degrees.

A gate insulating layer 140 preferably made of silicon nitride (SiNx) isformed on the gate lines 121.

A plurality of semiconductor islands 154 preferably made of hydrogenatedamorphous silicon (abbreviated to “a-Si”) are formed on the gateinsulating layer 140.

A plurality of ohmic contact islands 163 and 165 preferably made ofsilicide or n+ hydrogenated a-Si heavily doped with n type impurity areformed on the semiconductor islands 154. The ohmic contact islands 163and 165 are located in pairs on the semiconductor islands 154.

The lateral sides of the semiconductor islands 154 and the ohmiccontacts 163 and 165 are tapered, and the inclination angles thereof arepreferably in a range between about 30-80 degrees.

A plurality of data lines 171, a plurality of drain electrodes 175, anda plurality of storage capacitor conductors 177 are formed on the ohmiccontacts 163 and 165 and the gate insulating layer 140.

The data lines 171 for transmitting data voltages extend substantiallyin the longitudinal direction and intersect the gate lines 121. Aplurality of branches of each data line 171, which extend toward thedrain electrodes 175, form a plurality of source electrodes 173. Eachpair of the source electrodes 173 and the drain electrodes 175 areseparated from each other and opposite each other with respect to a gateelectrode 123. A gate electrode 123, a source electrode 173, and a drainelectrode 175 along with a semiconductor island 154 form a TFT having achannel formed in the semiconductor island 154 disposed between thesource electrode 173 and the drain electrode 175.

The storage capacitor conductors 177 overlap the expansions 127 of thegate lines 121.

The data lines 171, the drain electrodes 175, and the storage capacitorconductors 177 also include a low resistivity conductive layerpreferably made of Ag containing metal such as Ag and Ag alloy or Alcontaining metal such as Al and Al alloy. The data lines 171, the drainelectrodes 175, and the storage capacitor conductors 177 may have amultilayered structure including a low resistivity conductive layer andanother layer preferably made of Cr, Ti, Ta, Mo or their alloys such asMoW alloy having good physical, chemical and electrical contactcharacteristics with other materials such as ITO (indium tin oxide) andIZO (indium zinc oxide). A good exemplary combination of such layers isCr and Al—Nd alloy.

The lateral sides of the data lines 171, the drain electrodes 175, andthe storage capacitor conductors 177 are tapered, and the inclinationangle of the lateral sides with respect to a surface of the substrate110 ranges about 30-80 degrees.

The ohmic contacts 163 and 165 interposed only between the underlyingsemiconductor islands 154 and the overlying data lines 171 and theoverlying drain electrodes 175 thereon and reduce the contact resistancetherebetween.

A passivation layer 180 is formed on the data lines 171, the drainelectrodes 175, the storage conductors 177, and the exposed portions ofthe semiconductor islands 154. The passivation layer 180 is preferablymade of photosensitive organic material having a good flatnesscharacteristic, low dielectric insulating material such as a-Si:C:O anda-Si:O:F formed by plasma enhanced chemical vapor deposition (PECVD), orinorganic material such as silicon nitride. Alternatively, thepassivation layer 180 may includes both a SiNX film and an organic film.

The passivation layer 180 has a plurality of contact holes 185, 187 and189 exposing the drain electrodes 175, the storage conductors 177, andend portions 179 of the data lines 171, respectively. The passivationlayer 180 and the gate insulating layer 140 has a plurality of contactholes 182 exposing end portions 125 of the gate lines 121.

A plurality of pixel electrodes 190 and a plurality of contactassistants 92 and 97, which are preferably made of IZO or ITO, areformed on the passivation layer 180.

The pixel electrodes 190 are physically and electrically connected tothe drain electrodes 175 through the contact holes 185 and to thestorage capacitor conductors 177 through the contact holes 187 such thatthe pixel electrodes 190 receives the data voltages from the drainelectrodes 175 and transmits the received data voltages to the storagecapacitor conductors 177.

Referring back to FIG. 3, the pixel electrodes 190 supplied with thedata voltages generate electric fields in cooperation with the commonelectrode 270 on the other panel 200, which reorient liquid crystalmolecules in the liquid crystal layer 3 disposed therebetween.

As described above, a pixel electrode 190 and a common electrode 270form a liquid crystal capacitor C_(LC), which stores applied voltagesafter turn-off of the TFT Q. An additional capacitor called a “storagecapacitor,” which is connected in parallel to the liquid crystalcapacitor C_(LC), is provided for enhancing the voltage storingcapacity. The storage capacitors are implemented by overlapping thepixel electrodes 190 with the gate lines 121 adjacent thereto (called“previous gate lines”). The capacitances of the storage capacitors,i.e., the storage capacitances are increased by providing the expansions127 at the gate lines 121 for increasing overlapping areas and byproviding the storage capacitor conductors 177, which are connected tothe pixel electrodes 190 and overlap the expansions 127, under the pixelelectrodes 190 for decreasing the distance between the terminals.

The pixel electrodes 190 overlap the gate lines 121 and the data lines171 to increase aperture ratio but it is optional.

The contact assistants 92 and 97 are connected to the exposed endportions 125 of the gate lines 121 and the exposed end portions 179 ofthe data lines 171 through the contact holes 182 and 189, respectively.The contact assistants 92 and 97 are not requisites but preferred toprotect the exposed portions 125 and 179 and to complement theadhesiveness of the exposed portion 125 and 179 and external devices.

According to another embodiment of the present invention, the pixelelectrodes 190 are made of transparent conductive polymer. For areflective or transflective LCD, the pixel electrodes 190 include opaquereflective metal.

A TFT array panel for an LCD according to another embodiment of thepresent invention will be described in detail with reference to FIGS. 9,10A and 10B.

FIG. 9 is a layout view of an exemplary TFT array panel for an LCDaccording to another embodiment of the present invention, and FIGS. 10Aand 10B are sectional views of the TFT array panel shown in FIG. 9 takenalong the line XA-XA′ and the line XB-XB′, respectively.

As shown in the figures, a layered structure of a TFT array panel of anLCD according to this embodiment is almost the same as that shown inFIGS. 7 and 8. That is, a plurality of gate lines 121 including aplurality of gate electrodes 123 are formed on a substrate 110, and agate insulating layer 140 is formed thereon. A plurality ofsemiconductor stripes 151 including a plurality of extensions 154corresponding to the semiconductor islands 154 shown in FIGS. 7 and 8are formed on the gate insulating layer 140, and a plurality of ohmiccontact stripes 161 including a plurality of extensions 163corresponding to the ohmic contact islands 163 shown in FIGS. 7 and 8and a plurality of ohmic contact islands 165 are formed on thesemiconductor stripes 151. A plurality of data lines 171 including aplurality of source electrodes 173, a plurality of drain electrodes 175,and a plurality of storage capacitor conductors 177 are formed on theohmic contacts 161 and 165, and a passivation layer 180 is formedthereon. A plurality of contact holes 182, 185, 187 and 189 are providedat the passivation layer 180 and/or the gate insulating layer 140, and aplurality of pixel electrodes 190 and a plurality of contact assistants92 and 97 are formed on the passivation layer 180.

Different from the TFT array panel shown in FIGS. 7 and 8, the TFT arraypanel according to this embodiment provides a plurality of storageelectrode lines 131, which are separated from the gate lines 121, on thesame layer as the gate lines 121, and overlaps the storage electrodelines 131 with the storage capacitor conductors 177 to form storagecapacitors without expansions of the gate lines 121. The storageelectrode lines 131 are supplied with a predetermined voltage such asthe common voltage. The storage electrode lines 131 along with thestorage capacitor conductors 177 may be omitted if the storagecapacitance generated by the overlapping of the gate lines 121 and thepixel electrodes 190 is sufficient.

In addition, as well as the semiconductor stripes 151 and the ohmiccontacts 161 and 165, a plurality of semiconductor islands 157 and aplurality of ohmic contacts 167 thereover are provided between thestorage conductors 177 and the gate insulating layer 140.

The semiconductor stripes and islands 151 and 157 have almost the sameplanar shapes as the data lines 171, the drain electrodes 175 and thestorage capacitor conductors 177 as well as the underlying ohmiccontacts 161, 165 and 167, except for the extensions 154 where TFTs areprovided. In particular, the semiconductor islands 157, the ohmiccontact islands 167 and the storage conductors 177 have substantiallythe same planar shape. The semiconductor stripes 151 include someexposed portions, which are not covered with the data lines 171, thedrain electrodes 175 and the storage conductors 177, such as portionslocated between the source electrodes 173 and the drain electrodes 175.

FIG. 11 is a sectional view of an LCD according to another embodiment ofthe present invention, and FIGS. 12 to 15 illustrate pixel arrangementsof LCDs according to embodiments of the present invention.

As shown in FIG. 11, an LCD according to another embodiment of thepresent invention includes a lower panel 100, an upper panel 200 facingthe lower panel 200, and a liquid crystal layer 3 interposed between thelower and the upper panels and containing liquid crystal moleculesaligned in a predetermined direction. The LCD further includes upper andlower polarizers 12 and 22, and upper and lower compensation films 13and 23. The liquid crystal molecules vary in their orientations underthe application of electric fields. The transmittance of the light ischanged depending upon the orientations of the liquid crystal molecules.

The lower panel 100 includes a lower substrate 110 preferably made of atransparent insulating material such as glass, a plurality of thin filmtransistors TFT formed on the lower substrate 110, and a plurality ofpixel electrodes 190 connected to the TFTs and preferably made of atransparent conductive material such as ITO and IZO. Each TFT switchesdata voltages applied to the pixel electrode 190.

The lower compensation film 13 and the lower polarizer 12 are attachedto the outer surface of the lower substrate 110. The lower compensationfilm 13 has biaxiality or uniaxiality. The lower compensation film 13may be omitted.

The upper panel 200 includes an upper substrate 210 preferably made of atransparent insulating material such as glass, a black matrix 220defining a plurality of pixel areas arranged in a matrix, a plurality ofred, green and blue color filters 230R, 230G and 230B formed in thepixel areas defined by the black matrix 220, and a common electrode 270preferably made of a transparent conductive material such as ITO andIZO.

The red, green and blue color filters 230R, 230G and 230B are arrangedin turn. The pixel areas without any of the red, green and blue colorfilters 230R, 230G and 230B represent white pixel areas W, which equallyintercept or pass all the components of incident light. Since the whitepixel area W has no color filter, the inner surface of the color filterpanel 200 on the white pixel area W has smaller height than on the otherpixel areas R, G and B and the cell gap of the white pixel area W islarger than that at the other pixel areas.

In this specification, the term “pixel” indicates a basic functionalelement for displaying images, which includes a pixel electrode 190, aportion of the common electrode 270 opposite the pixel electrode 190, aportion of the liquid crystal layer 3 located between the pixelelectrode 190 and the corresponding portion of the common electrode 270,a TFT, and a color filter 230R, 230G or 230B. In addition, the term“pixel area” means the area occupied by a pixel. However, forconvenience of description, the two terms “pixel” and “pixel area” willnot be distinctly used in this specification.

Referring to FIG. 12, the numbers of the red, green, blue and whitepixels areas R, G, B and W are the same. The red, green, blue and whitepixel areas R, G, B and W are arranged in turn along the row direction.Each of the blue pixel areas B and the white pixel areas W has a sizeequal to about half of each of the red pixel areas R and the green pixelareas G. Therefore, the sum of one white pixel area W and one blue pixelarea B is nearly the same as one red pixel area R or one green pixelarea G.

Referring to FIG. 13, a 2×3 pixel matrix including identical pixelsforms a dot which is a basic element of an image. The first pixel rowincludes red, blue and green pixels arranged in sequence, and the secondpixel row includes green, white and red pixels arranged in sequence.

The arrangement of the pixels shown in FIG. 14 is almost the same asthat shown in FIG. 13 except that the blue pixel B is enlarged, whilethe white pixel W is reduced.

The pixel arrangement shown in FIG. 15 is almost the same as that shownin FIG. 13 except that portions of the black matrix BM surrounding thewhite pixel W is enlarged to have a width wider than other portions,which is established to hide the disclination lines generated due to theheight difference.

The upper compensation film 23 and the upper polarizer 22 are attachedto the outer surface of the upper substrate 210. The upper compensationfilm 23 has biaxiality or uniaxiality. The upper compensation film 23may be omitted.

Since the color filter 230R, 230G and 230B transmits one thirds ofincident light the light transmittance of a white pixel is about threetimes that of other color pixels. In this embodiment, since one dotincludes red, green, blue and white pixels, the optical efficiency isimproved without increasing the total area of the dot.

Assume that the amount of the light passing through the lower polarizer12 is one.

For a dot including three pixels, i.e., red, green and blue pixels, thearea of each pixel is one thirds of the total area of the dot. Since thelight transmittance of the color filter is one thirds, the total lighttransmittance of the dot is equal to ⅓×⅓+⅓×⅓+⅓×⅓=⅓≈33.3%.

For a dot shown in FIG. 12, the area of each of red and green pixels isone thirds of the total area, while the area of each of blue and whitepixels is one sixths of the total area. Since the light transmittance ofthe white pixel is one, while that of the other pixels is one thirds,the total light transmittance of the dot equals to⅓×⅓+⅓×⅓+⅙×⅓+⅙×1={fraction (4/9)}≈44.4%. Accordingly, the brightness isincreased to be about 1.5 times compared with a three-color LCD.

Although the area of the blue pixel is smaller than the red pixel or thegreen pixel, the variation of the amount of the blue light is relativelyinsensitive to a person compared with red and green light, and hence,the influence of the areal reduction on the image quality is relativelysmall.

However, the areal reduction of the blue pixel gives slight deformationin the images, that is, it makes the images yellowish.

In order to solve such a problem, the light source 341 emits a lightwith increased blue component to prevent yellowish images.

The light emitted from the light source 341 of the backlight unit 340shown in FIG. 2 has a color coordinate (x, y) where x ranges from about0.31 to about 0.34 and y ranges from about 0.32 to about 0.35. Such alight contains the blue component more than the light emitted from alight source for a conventional LCD backlight. In order to obtain such alight source, the blue color emitting material to be contained in thelight source 341 should be increased by a predetermined amount.

FIG. 16 is a graph showing an exemplary light spectrum of a light sourceaccording to an embodiment of the present invention. Compared with thecurve for a conventional light source represented by “blue 1”, thecurves represented by “blue 1.09” and “blue 1.18” show enhanced peaks atwavelength in a range of about 440-470 nm, which indicates blue light,and decreased peaks at wavelength in a range of about 620-650 nm, whichindicates red light.

Meanwhile, since the white pixel W has no color filter, the light out ofthe white pixel W from the light source 531 may look bluish. However,the larger cell gap of the white pixel W, which makes the incident lightyellowish, prevents the light from being bluish.

FIGS. 17 and 18 are sectional views of color filter array panels for anLCD according to other embodiments of the present invention.

Referring to FIG. 17, a color filter array panel 200 includes atransparent insulating substrate 210, a black matrix 220 formed on theinsulating substrate 210 having a plurality of apertures defining pixelareas, a plurality of red, green, blue and transparent color filters230R, 230G, 230B and 230W formed in respective pixel areas, an overcoat250 formed on the color filters 230R, 230G, 230B and 230W, and a commonelectrode 270 formed on the overcoat 250. It is preferable that thetransparent color filters 230W include a transparent organic materialsuch as a photosensitive material without pigment.

A color filter array panel 200 shown in FIG. 18 includes no transparentcolor filter.

Instead, portions of an overcoat 250 in white pixel areas W have largerthickness than other portions thereof to make the height difference ofthe surface equal to or less than about 0.0.2 microns. Accordingly, thecell gap for all pixels is nearly uniform, and the color filter arraypanel 200 is manufactured by relatively simple process compared withthat shown in FIG. 17 since the step of forming a transparent colorfilter 230W is omitted.

The color filter array panels 200 shown in FIGS. 17 and 18 reduces stepdifference between the white pixels W and the other pixels R, G and B byproviding the transparent color filters 230W or by increasing thethickness of the overcoat 250 at the white pixels W.

The reduced step difference and the uniform cell gap prevent theyellowish light of the white pixel W and the discilnation lines at thesteps.

Preferably, the cell gap or the thickness of the liquid crystal layer isequal to about 3.7 microns and the thickness of the color filters isabout 1.5 to 1.6 microns.

FIG. 19 is a graph illustrating the response time as a function of thecell gap of an LCD.

As shown in FIG. 19, the response time become reduced as the increase ofthe cell gap. When the cell gap reaches about 3.7 microns, the responsetime has a minimum value. As the cell gap goes away from 3.7 microns,the response time becomes increased again.

FIG. 20 is a sectional view of an LCD according to another embodiment ofthe present invention.

Referring to FIG. 20, an LCD according to this embodiment includes a TFTarray panel 100, a color filter array panel 200, and a liquid crystallayer 3 interposed therebetween.

The color filter array panel 200 includes an upper panel 210 preferablymade of a transparent insulating material such as glass, a black matrix220 formed on the upper panel 210 and defining a plurality of pixelareas arranged in a matrix, a plurality of red, green and blue colorfilters 230R, 230G and 230B disposed substantially in the pixel areas,an overcoat 250 formed on the color filters 230R, 230G and 230B, and acommon electrode 270 preferably made of a transparent conductivematerial such as ITO and IZO and having a plurality of cutouts 271.

The red, green and blue color filters 230R, 230G and 230B are arrangedin turn. The pixel areas without any of the red, green and blue colorfilters 230R, 230G and 230B represent white pixel areas W, which equallyintercept or pass all the components of incident light. Since the whitepixel area W has no color filter, the inner surface of the color filterpanel 200 on the white pixel area W form a basin.

The TFT array panel 100 may have a structure shown in FIGS. 5 and 6.That is the TFT array panel 100 includes a plurality of gate electrodes123 formed on an insulating substrate 110, a gate insulating layer 140formed on the gate electrodes 123, a plurality of semiconductors 154preferably made of amorphous silicon formed on the gate insulating layer140 opposite the gate electrodes 123, a plurality of ohmic contacts 163and 165 formed on the semiconductors 154, a plurality of source anddrain electrodes 173 and 175 respectively formed on the ohmic contacts163 and 165, a protective layer 180 covering the source and the drainelectrodes 173 and 175 and having a plurality of contact holes 181exposing the drain electrodes 175, and a plurality of pixel electrodesconnected to the drain electrodes 175 through the contact holes 181 andhaving a plurality of cutouts 191.

The surface of the protective layer 180 is protruded at the white pixelW to form a plateau.

The basins of the color filter array panel and the plateaus of the TFTarray panel face each other such that the white pixels W have nearly thesame cell gap as the other pixels.

The above-described protective layer 180 is formed by photolithographywith a photo mask having a translucent area as well as a transparentarea and an opaque area. After depositing the protective layer 180 andcoating a photoresist film thereon, the photo mask is aligned such thatthe transparent area and the opaque area face the contact hole 181 andthe white pixel area W, while the translucent area faces remainingareas. After exposure and development, a portion of the photoresist filmon the contact hole 180 is removed to expose a portion of the protectivelayer 180, a portion on the white pixel area W is left over, and theother portions have reduced thickness. The contact hole 181 is formed byetching using the photoresist film as an etching mask, and thephotoresist film suffers ashing such that the portions of thephotoresist film with reduced thickness is removed to expose portions ofthe protective layer 180. Consequently, the photoresist film is leftover only on the white pixel area W. The protective layer 180 is etchedusing the photoresist film as an etching mask such that the exposedportions of the protective layer 180 are thinned to form a plateau onthe white pixel area W.

Meanwhile, a plurality of photolithography steps are introduced inmanufacturing the TFT array panel 100, and the use of a photo maskhaving translucent areas as well as transparent and opaque areas reducethe number of photolithography steps. Several layers having differentpatterns can be made by using a photoresist film havingposition-dependent thickness made by using the photo mask. For instance,the semiconductors 154, the ohmic contacts 163 and 165, and the sourceand the drain electrodes 163 and 165 are formed by using such aphotoresist film, and thus, the TFT array panel 100 can be completedusing less masks compared with the case using photo masks having onlytransparent and opaque areas. In this case, the source and the drainelectrodes 163 and 165, and the ohmic contacts have substantially thesame planar shape, and the semiconductors 154 except for the channelregion has substantially the same planar shape as the source and thedrain electrodes 163 and 165.

The TFT array panel 100 and the color filter array panel 200 are alignedto be assembled. Thereafter, a liquid crystal material 3 is injectedinto a gap between the panels 100 and 200 and subject to verticalalignment. A pixel region, which indicates a portion of the liquidcrystal layer 3 in a pixel, is partitioned into a plurality of domainsby the cutouts 191 and 271 of the pixel electrode 190 and the commonelectrode 270. The domains are classified into four kinds depending uponthe tilt directions of the liquid crystal molecules therein uponapplication of electric field. The several kinds of the domains givewide viewing angle.

FIGS. 21 to 23 illustrate pixel arrangements for an LCD according toother embodiments of the present invention.

Referring to FIGS. 21 to 23, an LCD according to this embodimentincludes red, blue and green pixels R, B and G arranged like a PenTileMatrix and white pixels W adjacent to the blue pixels B.

For a descriptive purpose, it is considered a set of pixels includingblue and white pixels B and W adjacent to each other, a pair of redpixels R obliquely facing each other across the blue and the whitepixels B and W, and a pair of green pixels G obliquely facing each otheracross the blue and the white pixels B and W and adjacent to the redpixels R. Then, the pixel arrangements shown in FIGS. 21 to 23 areobtained by repeatedly arranging such sets of pixels. It is noted thatthe relative positions of the blue pixel B and the white pixel W in twosets of pixels adjacent in a column direction or in a row direction arereversed.

The blue pixel B and the white pixel W shown in FIG. 21 have rectangularshapes as the red and the green pixels R and G and are arranged in thecolumn direction to form a separate column.

Alternatively, the blue pixel B and the white pixel W shown in FIGS. 22and 23 have isosceles triangular shapes, and a pair of the blue and thewhite pixels B and W face their bottom sides to form a diamond shape.The blue and the white pixels B and W shown in FIG. 22 are arranged inthe column direction, while those shown in FIG. 23 are arranged in a rowdirection. Accordingly, a boundary line between the blue pixel B and thewhite pixel W shown in FIG. 22 match the boundary line between the pixelrows, while a boundary line between the blue pixel B and the white pixelW shown in FIG. 23 match the boundary line between the pixel columns.

Referring to FIGS. 21 and 22, the relative positions of the blue pixel Band the white pixel W in two sets of pixels adjacent in the rowdirection are reversed. However, referring to FIG. 23, the relativepositions of the blue pixel B and the white pixel W in two sets ofpixels adjacent in the column direction are reversed.

In this arrangement, the red pixels R in adjacent two columns arelocated in different rows, while those in adjacent rows are located indifferent columns. Likewise, the green pixels in adjacent two columnsare placed in different rows, while those in adjacent rows are locatedin different columns. In addition, the blue pixels B or the white pixelsW in two sets adjacent in the row direction are located in differentrows as shown in FIGS. 21 and 22, or alternatively, the blue pixels B orthe white pixels W in two sets adjacent in the column direction arelocated in different columns as shown in FIG. 23. Accordingly, the samecolor pixels, particularly the blue pixels are arranged in zigzag alongthe column direction and the row direction.

A dot for displaying an image preferably includes an above-described setof pixels including a pair of blue and white pixels B and W, a pair ofred pixels R, and a pair of green pixels G.

However, when using rendering, a dot may include a pair of blue andwhite pixels B and W and a pair of red and green pixels in a column.

In any cases, these pixel arrangements prevent vertical line patterngenerated in a three color LCD where the same color pixels such as bluepixels are arranged in the column direction and the resolution is notsufficiently high. Therefore, an LCD having a PenTile Matrix pixelarrangement realizes improved image quality.

FIG. 24 is a picture for illustrating the visibility of an LCD havingthe pixel arrangement shown in FIG. 21. As shown in FIG. 24, no verticalline pattern is recognizable.

Exemplary TFT array panels for an LCD having the pixel arrangementsshown in FIGS. 21 and 22 will be now described with reference to FIGS.25 and 26.

FIG. 25 is a layout view of a TFT array panel for an LCD according toanother embodiment of the present invention, and FIG. 26 is a sectionalview of the TFT array panels shown in FIG. 25 taken along the lineXXVI-XXVI′.

As shown in FIGS. 25 and 26, a layered structure of a TFT array panel ofan LCD according to this embodiment is almost the same as that shown inFIGS. 5 and 6. That is, a plurality of gate lines 121 including aplurality of gate electrodes 123 are formed on a substrate 110, and agate insulating layer 140, a plurality of semiconductor islands 154, anda plurality of ohmic contact islands 163 and 165 are sequentially formedthereon. A plurality of data lines 171 including a plurality of sourceelectrodes 173 and a plurality of drain electrodes 175 are formed on theohmic contacts 161 and 165 and the gate insulating layer 140, and apassivation layer 180 is formed thereon. A plurality of contact holes182, 185 and 189 are provided at the passivation layer 180 and/or thegate insulating layer 140, and a plurality of pixel electrodes 190 and aplurality of contact assistants 92 and 97 are formed on the passivationlayer 180.

Referring to FIGS. 25 and 26, the pixel electrodes 190 of the pixels R,G, B and W resemble the shapes of the corresponding pixels shown in FIG.22. A plurality of storage lines 131 extending substantially parallel tothe gate lines 121 and made of the same material as the gate wire areformed on the substrate 110. The gate lines 121 and the storage lines131 are located near the boundaries of the pixel rows, and the pixelelectrodes 190 and the TFTs are symmetrically arranged with respect tothe storage lines 131. The storage lines 131 overlap the pixelelectrodes 190 adjacent thereto to form a plurality of storagecapacitors.

Referring back to FIGS. 1 and 2, the gray voltage generator 800generates two sets of a plurality of gray voltages related to thetransmittance of the pixels and is provided on the data PCB 550. Thegray voltages in one set have a positive polarity with respect to thecommon voltage Vcom, while those in the other set have a negativepolarity with respect to the common voltage Vcom.

The gate driver 400 preferably includes a plurality of integratedcircuit (IC) chips mounted on the respective gate FPC films 410. Thegate driver 400 is connected to the gate lines G₁-G_(n) of the panelassembly 300 and synthesizes the gate-on voltage Von and the gate offvoltage Voff from the driving voltage generator 700 to generate gatesignals for application to the gate lines G₁-G_(n).

The data driver 500 preferably includes a plurality of IC chips mountedon the respective data FPC films 510. The data driver 500 is connectedto the data lines D₁-D_(m) of the panel assembly 300 and applies datavoltages selected from the gray voltages supplied from the gray voltagegenerator 800 to the data lines D₁-D_(m).

According to another embodiment of the present invention, the IC chipsof the gate driver 400 and/or the data driver 500 are mounted on thelower panel 100, while one or both of the drivers 400 and 500 areincorporated along with other elements into the lower panel 100according to still another embodiment. The gate PCB 450 and/or the gateFPC films 410 may be omitted in both cases.

The signal controller 600 controlling the drivers 400 and 500, etc. isprovided on the data PCB 550 or the gate PCB 450.

Now, the operation of the LCD will be described in detail.

The signal controller 600 is supplied with RGB image signals R, G and Band input control signals controlling the display thereof such as avertical synchronization signal Vsync, a horizontal synchronizationsignal Hsync, a main clock MCLK, and a data enable signal DE, from anexternal graphic controller (not shown). After generating gate controlsignals CONT1 and data control signals CONT2 and processing the imagesignals R, G and B suitable for the operation of the panel assembly 300on the basis of the input control signals and the input image signals R,G and B, the signal controller 600 provides the gate control signalsCONT1 for the gate driver 400, and the processed image signals R′, G′and B′ and the data control signals CONT2 for the data driver 500.

The gate control signals CONT1 include a vertical synchronization startsignal STV for informing of start of a frame, a gate clock signal CPVfor controlling the output time of the gate-on voltage Von, and anoutput enable signal OE for defining the width of the gate-on voltageVon. The data control signals CONT2 include a horizontal synchronizationstart signal STH for informing of start of a horizontal period, a loadsignal LOAD or TP for instructing to apply the appropriate data voltagesto the data lines D₁-D_(m), an inversion control signal RVS forreversing the polarity of the data voltages (with respect to the commonvoltage Vcom) and a data clock signal HCLK.

The data driver 500 receives a packet of the image data R′, G′ and B′for a pixel row from the signal controller 600 and converts the imagedata R′, G′ and B′ into the analogue data voltages selected from thegray voltages supplied from the gray voltage generator 800 in responseto the data control signals CONT2 from the signal controller 600.

Responsive to the gate control signals CONT1 from the signals controller600, the gate driver 400 applies the gate-on voltage Von to the gateline G₁-G_(n), thereby turning on the switching elements Q connectedthereto.

The data driver 500 applies the data voltages to the corresponding datalines D₁-D_(m) for a turn-on time of the switching elements Q (which iscalled “one horizontal period” or “1H” and equals to one periods of thehorizontal synchronization signal Hsync, the data enable signal DE, andthe gate clock signal CPV). Then, the data voltages in turn are suppliedto the corresponding pixels via the turned-on switching elements Q.

The difference between the data voltage and the common voltage Vcomapplied to a pixel is expressed as a charged voltage of the LC capacitorC_(LC), i.e., a pixel voltage. The liquid crystal molecules haveorientations depending on the magnitude of the pixel voltage and theorientations determine the polarization of light passing through the LCcapacitor C_(LC). The polarizers convert the light polarization into thelight transmittance.

By repeating this procedure, all gate lines G₁-G_(n) are sequentiallysupplied with the gate-on voltage Von during a frame, thereby applyingthe data voltages to all pixels. When the next frame starts afterfinishing one frame, the inversion control signal RVS applied to thedata driver 500 is controlled such that the polarity of the datavoltages is reversed (which is called “frame inversion”). The inversioncontrol signal RVS may be also controlled such that the polarity of thedata voltages flowing in a data line in one frame are reversed (which iscalled “line inversion”), or the polarity of the data voltages in onepacket are reversed (which is called “dot inversion”).

Various types of inversions for an LCD according to embodiments of thepresent invention are described in detail with reference to FIGS. 27-29.

The inversions shown in FIGS. 27-29 can be adapted to the pixelarrangements shown in FIGS. 4A and 4B, 5A and 5B, 13-15, 21-23. Asdescribed above, the pixel arrangements are formed by repeatedlyarranging a group of pixels including six pixels, i.e., two pixels nearthe center and four pixels disposed at both sides of the two pixels.Hereinafter, the two pixels near the center are referred to as centerpixels, and the remaining four pixels are referred to as peripheralpixels. For a three color LCD, the center pixels represent one of red,green and blue colors, while the peripheral pixels represent theremaining two colors. For a four color LCD, the center pixels are blueand white pixels B and W, while the peripheral pixels are red and greenpixels R and G.

FIG. 27 illustrates a column inversion that makes two adjacent pixels ina row have opposite polarity and two adjacent pixels in a column haveequal polarity.

As shown in FIG. 27, since the pixels representing the same color in apixel group have equal polarity, flicker, which is generated in dotinversion, is not generated. In addition, since the adjacent pixels in arow have opposite polarity and the adjacent pixels in a row for a coloror a dot also have opposite polarity, horizontal cross-talk is preventedsuch that the characteristics of horizontal display are improved.

FIG. 28 illustrates a 2×1 inversion that makes two adjacent pixels in arow have opposite polarity and the polarity in a column alternate everytwo pixels.

The inversion shown in FIG. 28 also prevents the flicker since thepixels representing the same color in a pixel group have equal polarity.Since the adjacent pixels in a row have opposite polarity and theadjacent pixels in a row for a color also have opposite polarity,horizontal cross-talk is prevented such that the characteristics ofhorizontal display are improved. Moreover, since the polarity for anyone color is inverted every pixel in a column, vertical cross-talk isalso prevented.

FIG. 29 illustrates a 2×2 inversion that the polarity in a column and ina row is alternate every two pixels.

As shown in FIG. 28, the center pixels have equal polarity while theperipheral pixel pairs representing the same color have differentpolarity. However, since the peripheral pixel pairs representingcorresponding colors have both positive and negative polarity, thebrightness is averaged to be uniform and thus the flicker is prevented.Since the polarity in a row for a color is inverted every two pixels,the characteristics of horizontal display are improved. Furthermore,since the polarity for any one color is inverted in a column, verticalcross-talk is also prevented.

Although preferred embodiments of the present invention have beendescribed in detail hereinabove, it should be clearly understood thatmany variations and/or modifications of the basic inventive conceptsherein taught which may appear to those skilled in the present art willstill fall within the spirit and scope of the present invention, asdefined in the appended claims.

1. A liquid crystal display comprising: an array of a plurality of setsof pixels, each set including blue and white pixels adjacent to eachother, a pair of red pixels obliquely facing each other across the blueand the white pixels, and a pair of green pixels obliquely facing eachother across the blue and the white pixels and adjacent to the redpixels, each pixel including a pixel electrode and a thin filmtransistor; a plurality of gate lines extending in a row direction fortransmitting a gate signal to the pixels; and a plurality of data linesextending in a column direction for transmitting data signals to thepixels.
 2. The liquid crystal display of claim 1, wherein the blue pixeland the white pixel in a set of pixels have equal polarity, the redpixels in the set have equal polarity, and the green pixels in the sethave equal polarity.
 3. The liquid crystal display of claim 2, whereinthe polarity of the pixels are subject to column inversion.
 4. Theliquid crystal display of claim 2, wherein the polarity of the pixelsare subject to 2×1 inversion.
 5. The liquid crystal display of claim 1,wherein the blue pixel and the white pixel in a set of pixels have equalpolarity, the red pixels in the set have opposite polarity, and thegreen pixels in the set have opposite polarity.
 6. The liquid crystaldisplay of claim 5, wherein the polarity of the pixels are subject to2×1 inversion.
 7. The liquid crystal display of claim 1, whereinrelative positions of the blue pixel and the white pixel in two sets ofpixels adjacent in a column direction or in a row direction arereversed.
 8. The liquid crystal display of claim 1, wherein the pixelshave rectangular shapes and the blue and the white pixels are arrangedin the column direction to form a separate column.
 9. The liquid crystaldisplay of claim 1, wherein the blue pixel and the white pixel havetriangular shapes to form a diamond shape.
 10. The liquid crystaldisplay of claim 9, wherein a boundary line between the blue pixel andthe white pixel extends in the row direction or the column direction.11. The liquid crystal display of claim 1, wherein the red pixels inadjacent two columns are located in different rows and the red pixels inadjacent rows are located in different columns, wherein the green pixelsin adjacent two columns are placed in different rows and the greenpixels in adjacent rows are located in different columns, and whereineither the blue pixels or the white pixels in two sets of pixelsadjacent in the row direction are located in different rows, or the bluepixels or the white pixels in two sets adjacent in the column directionare located in different columns.
 12. The liquid crystal display ofclaim 1, wherein the liquid crystal display is driven by rendering. 13.The liquid crystal display of claim 1, further comprising a backlightunit providing light for the pixels, wherein light emitted from thebacklight unit has a color coordinate (x, y) where x ranges from about0.31 to about 0.34, and y ranges from about 0.32 to about 0.35.
 14. Theliquid crystal display of claim 1, wherein the red, green and bluepixels further comprise red, green and blue organic filters containingred, green and blue pigments, respectively, and the white pixels includetransparent organic filters.
 15. The liquid crystal display of claim 14,wherein the red, green, blue and white pixels further comprise a commonelectrode formed on the organic filters.
 16. The liquid crystal displayof claim 15, wherein the red, green, blue and white pixels furthercomprise an overcoat located between the organic filters and the commonelectrode.
 17. The liquid crystal display of claim 16, wherein thetransparent organic filter includes the same material as the overcoat.18. The liquid crystal display of claim 15, wherein the height of asurface of the overcoat is substantially uniform.
 19. The liquid crystaldisplay of claim 1, wherein the red, green, blue and white pixelsfurther comprise red, green and blue color filters, respectively, andthe red, green, blue and white pixels further comprise: a protectivelayer formed on the thin film transistors, having a plurality ofprotrusions, and facing the color filters; a common electrode formed onthe color filters; and a liquid crystal interposed between the pixelelectrode and the common electrode, wherein the protrusions are providedin the white pixels, and height of the common electrode is smaller atthe white pixel than at the red, the green and the blue pixels.
 20. Theliquid crystal display of claim 19, wherein distance between the commonelectrode and a surface of the protective layer is substantiallyuniform.
 21. The liquid crystal display of claim 14, wherein the pixelelectrodes and the common electrode have cutouts.
 22. A liquid crystaldisplay comprising: an array pixel including a plurality of pixelsarranged in a matrix, the plurality of pixels including a set of pixelsincluding a pair of center pixels adjacent to each other, and a pair offirst-color pixels and a pair of second-color pixels obliquely facingeach other across the center pixels, each pixel including a pixelelectrode and a thin film transistor; a plurality of gate linesextending in a row direction for transmitting a gate signal to thepixels; and a plurality of data lines extending in a column directionfor transmitting data signals to the pixels, wherein the pixels aresubject to polarity inversion.
 23. The liquid crystal display of claim22, wherein the center pixels in a set of pixels have equal polarity,the first-color pixels in the set have equal polarity, and thesecond-color pixels in the set have equal polarity.
 24. The liquidcrystal display of claim 23, wherein the polarity inversion includescolumn inversion.
 25. The liquid crystal display of claim 23, whereinthe polarity inversion includes 2×1 inversion.
 26. The liquid crystaldisplay of claim 22, wherein the center pixels in a set of pixels haveequal polarity, the first-color pixels in the set have oppositepolarity, and the second-color pixels in the set have opposite polarity.27. The liquid crystal display of claim 26, wherein the polarityinversion includes 2×1 inversion.
 28. The liquid crystal display ofclaim 22, wherein the center pixels represent blue color, and thefirst-color pixels and the second-color pixels represent green and redcolors, respectively.
 29. The liquid crystal display of claim 22,wherein the center pixels represent red color, and the first-colorpixels and the second-color pixels represent green and blue colors,respectively.
 30. The liquid crystal display of claim 22, wherein thecenter pixels represent blue and white colors, and the first-colorpixels and the second-color pixels represent green and red colors,respectively.
 31. The liquid crystal display of claim 22, wherein thecenter pixels have different saturation.
 32. The liquid crystal displayof claim 31, wherein the center pixels represent red color.